Swarm of Quakes Shakes Fairfield Area Northeast of San Francisco

A swarm of more than 25 earthquakes, the strongest magnitude 3.5 and seven of at least magnitude 3.0, shook an area near Fairfield, 40 miles northeast of San Francisco, on Thursday, and scientists said the temblors could continue for a few days.

No injuries or damage were reported, but many of the quakes were felt by residents in Fairfield, Pittsburg, Concord and Martinez. They were centered eight miles southeast of Fairfield, at a depth of 13 miles. The 3.5 quake took place at 7:39 a.m.

Rick Lester of the U.S. Geological Survey said the quakes may have been on the Kirby Hills fault, a part of the major Calaveras fault system that runs through the East Bay.

Lester said an earlier quake swarm in the same location, in the 1970s, lasted a month. But most swarms in the vicinity have not gone on so long. He said it is doubtful that larger quakes will occur in the series.